Thanks,

I will go about having a look at these at the weekend. Anything to squeeze extra miles from the little darling...

Argonought said:

What does your on-board computer say

I'd say yours is fine - although if you ALWAYS get a preheat fault then I'd get is sorted as you may well see even better mpg.

Remember if you get 3 good starts (without an error) then the fault should be cleared (mpg not degraded) but otherwise it will stay logged.

Only guessing about what's going on here but I'm sure not dreaming it

Click to expand...

hi argo on a long run i am getting as above 55-60..
around the doors 41-48 mph to be honest i am happy with that going to change the relay at some point....one day i will be 100% error free. only 2 two go air bag and preheat lol.....

ricnfiona said:

hi argo on a long run i am getting as above 55-60..
around the doors 41-48 mph to be honest i am happy with that going to change the relay at some point....one day i will be 100% error free. only 2 two go air bag and preheat lol.....

Click to expand...

I don't think there's much wrong with your Stilo

But that means the puzzle gets deeper as we now have:

2 owners who've noticed mpg improved after fixing pre-heat error
1 owner with a pre-heat error but still has good mpg

I wonder if it's connected with HOW the heater relay module goes faulty rather than simply having a pre-heat error recorded within the ECU :chin:

I wouldnt want to fall out with you guys either

JTD has no adaption, but if a fault code is recorded the signal is substituted for a constant figure eg water temp sensor signal fault, constant temp of say 65 degrees would be used by ecu, engine wont go into limp home but economy is effected.

However, how a pre-heat error would effect fuel economy I cant say.

One thing I noticed on my annual trip out of Norfolk this year (there be dragons outside Norfolk you know), was my fuel economy on my 200 mile journey. At 60 mph my first 100 miles averaged 57 mpg. I then gave her a clear out (hard acceleration and flush the exhaust) and the next 100 miles averaged 59 mpg. She also averaged 59 all the way home (200 miles) after virtually no use for a week.

Personally I think the exhaust causes some mpg problems by partial sooting up, the more you drive gently the more soot gets trapped in the exhaust and the more it restricts the exhaust gases until it is flushed out by hard acceleration. I didnt expect a 2mpg improvement after just 30 seconds hard acceleration, but I definately got it. A glow plug fault would cause more soot to be passed into the exhaust when cold, and warming up but the sort of figures for fuel improvements you guys are stating are way more than I experienced. However, if the ecu increases fuel delivery pressure or fuel quantity to try to counter a poor glow plug system then this would go hand in hand with what you say. Time to experiment with examiner me thinks.

it is very strange argo..........

after all the heater plugs ony get hot once every start then heat and compression keeps them hot.

it can only be ecu related possible but unlikely that one of the glow plug carbon electrodes is duff then it wouldn't keep the same heat as the other 3.

however i would think that if this happens then you would notice an erratic running engine.

the unburned diesel would get blown out into the exhaust and could cause the cat to fail (egg smell) as it did to my old Renault and a loss of power due to the cat collapsing

Hi all,

I've been reading all your posts and theorys about mpg on stilo jtd engine. I will put my share of experiences with fuel consumption on my 5dr.
First all, beware of course that de 5dr and the 3dr versions are different historys on consumptions, drag coefficient, weight can drop half liter I think.

My experience is, (and I had the pre-heat warning for a week, or intermitently):
- At hot days your engine temp rises quite fast, that and considering that you use the car a lot on cold starts, can drop half a liter or more on fuel consumption
- Of course, on hot days you probably dont use wipers so much, air ventilation, and so on, that improve mpg too of course (unless you use climate air )
- At roadway my stilo can take more variations off my mood, I can floor it 50% of the time, push it on and cruise at 140km/h or 150km/h and the overall consumption don't get hurt for more than 0,1l . On city drive, it's completely different, if I rev up 2nd or 3rd gear listening to some vibrant house music than I can drop from 51mpg for 44mpg just like that

Statistics:
- Never done 41mpg or less
- Never done 57mpg or higher

BTW, I read Jug saying that the car now rolls smooth at 5th gear cruising at 30mph. If I'm not mistaken at this speed the car must be at near 1k revolutions, that's no quite healthy for your engine. Some say that when cruising, especially with diesel high cc cars (1.9, 2.0, and so on) you should try not run under 1.5k revs. Below that, and near 1k can ironically decrease your mpg and reduce the lifetime of your engine.

Regards for all

I have a MW 2006 Dynamic, and my average is +/- 44 mpg, on a long trip this can go up to 55/58 mpg. This is a manually calculated figured based on actual fuel purchased and cum miles driven after each tank fill-up from new in December 2006. The on board computer shows my average as 42.4 mpg. Cruising at 60 mph on a flatish road, the onboard will show +/- 58 mpg. No mods or tweaks on this car, just a new egr valve a couple of months back.
I previously had a very nice 3 dr Dynamic and that returned around 44/46 mpg. over a 3 year period - again long trips were 58/60 mpg.
On both cars I ran the dual zone a/c constantly on fully auto all year round - keeps the mist down in the wet and cold winter!

RJose said:

BTW, I read Jug saying that the car now rolls smooth at 5th gear cruising at 30mph. If I'm not mistaken at this speed the car must be at near 1k revolutions, that's no quite healthy for your engine. Some say that when cruising, especially with diesel high cc cars (1.9, 2.0, and so on) you should try not run under 1.5k revs. Below that, and near 1k can ironically decrease your mpg and reduce the lifetime of your engine.

Click to expand...

Obviously no harm comes to the engine when it idles so it follows that if it can provide minimal drive to the transmission at the same time then that should be OK too (as you say, at 30mph in 5th you're basically very close to idle speed). What you shouldn't do is provide heavy load to the engine at such low revs - like flooring the accelerator or trying to climb a hill :shakehead:

There's another reason for that too which is related to fuel consumption which is that the engine is most fuel efficient at converting diesel to energy at 2000rpm (max torque on the standard map). That's why holding 2000rpm is so important for climbing hills. Once you get to the top, with injectors effectively shut-down, you get to go down the other side for free (subject to concerns of safely and legality of course ) which I've found very effective for achieving good average mpg results.

Changing down to hold 2000rpm on the flat doesn't make much sense though since the engine is only trying to overcome the resistance of the atmosphere plus that of all moving parts (which you make worse if you change down). I'd say ideal is the highest gear that doesn't strain the engine.

Best theoretical speed for low fuel consumption is 62mph in top (2000rpm). Classic physics dictates you must get better fuel consumption at lower speeds (which of course you will) but it just takes rather a long time to get to your destination

Well my Stilo MW has just done 790 miles at an average 49mph and 41.9mpg. This is at least 6-7mpg down on what it used todo when i first had it.
I think my current tyres are having a impact on the mpg as they do drone and i do need to have the balancing done and maybe have the tracking checked too.

Hi Argo, I love to read your posts. Been following your posts everywhere I go, you're very good and you've got always something to say, in my opinion you got experience, you are curious and you like to help.
Sorry, I called you Jug, that was a mistake, my bad
Once again, love to read your arguments, and I think you're mostly right, but let me only complement on one thing, just because the car can idle with no harm that doesn't mean you can travel on the same rev has idle. The engine effort to give power to the wheels and keep the car moving is by far higher than just idling. When cruising you have several opposite forces that you don't have in idle mode, and on that low speed your car is struggling to keep it going. I don't mean that you can't run on that rev or speed with that gear, I do low revs all the time, I rarely rev higher than 2k (just when I'm flooring it), but of course I know that, on so low rev speeds, I can only accelerate very slowly and never put the car on climb hill stress
Nevertheless I just saw that you have the stilo remapped, ok, 150hp must be different from the 115hp, I'm sure of that Maybe the car get a little different behavior. Feel free to share your experience with the 150 stalions

ManOfStilo said:

I have a MW 2006 Dynamic, and my average is +/- 44 mpg, on a long trip this can go up to 55/58 mpg. This is a manually calculated figured based on actual fuel purchased and cum miles driven after each tank fill-up from new in December 2006. The on board computer shows my average as 42.4 mpg. Cruising at 60 mph on a flatish road, the onboard will show +/- 58 mpg. No mods or tweaks on this car, just a new egr valve a couple of months back.
I previously had a very nice 3 dr Dynamic and that returned around 44/46 mpg. over a 3 year period - again long trips were 58/60 mpg.
On both cars I ran the dual zone a/c constantly on fully auto all year round - keeps the mist down in the wet and cold winter!

Click to expand...

Rechecked my numbers on the onboard, it's actually showing an average of 45.5 mpg, and my manual calculations give 44.6 mpg. Better than my memory!!

Hi,

I read most of the posts of this topic. It already gave me many ideas. I ended up at this forum via Google, as I too do have a mpg (of km/l, as I'm Dutch) problem with my Stilo (MW, jtd 115). I already tried cleaning the MAF. That didn't have any effect. I've had the EGR valve cleaned without any noticable effect. Yesterday I decided to order a MAP sensor that I'll try to fit this afternoon.

I'll keep you informed about the effects. Someone also gave me the advice to check the timing of the cam belt (is that the proper English word for it?). If changing the MAP doesn't work I might have that done.

Best regards, Martijn

Back again. Changed the MAP 2 hours ago. After that I took the battery pole off for a while. After that I went for a test drive. At first it seemed to idle a lot smoother and realy seemed to be more economical, about 55 mpg at 67 mph (110 km/h) with pretty strong headwind. Then on the return I accelerated to the max to get on to the motorway. After that, with tailwind I just made 44 mpg at 75 mph (120 km/h). I'm afraid I lost it... Anyone????

mfranke said:

I'm afraid I lost it... Anyone????

Click to expand...

You mean with your right foot

You need use trip 'B' to take an average over 30 miles or more to really come to any sensible conclusions on economy.

I drove about 40 miles initialy. During the weekend I did about 100 miles. My conclusion is that only on low speeds fuel economy has slightly improved (due to blocking EGR? I did that after my first (unsuccesful) test drive with the new MAP).

Does anyone know if it's likely that the MAF doesn't give the right signals even though it's spotless? (I cleaned it quite neatly, it was very dirty due to a damaged air filter. I replaced that immediatly after I bought the car. Cleaning the MAF didn't have any effect).

well just cleanned the egr valve ,new air filter, oil filter and cleaned the maf sensor new concentric clutch slave and its definatley better.

NumanR said:

I didnt expect a 2mpg improvement after just 30 seconds hard acceleration, but I definately got it. A glow plug fault would cause more soot to be passed into the exhaust when cold, and warming up but the sort of figures for fuel improvements you guys are stating are way more than I experienced. However, if the ecu increases fuel delivery pressure or fuel quantity to try to counter a poor glow plug system then this would go hand in hand with what you say.

Click to expand...

I now accept I was completely wrong in thinking the JTD adapts to driving style because if it does then it completely forgets about it the next day

What I've now discovered is my JTD starts off (when cold) producing very poor mpg figures - and continues like this even when the engine is fully warmed. However, something very strange happens when you give it a bit of right foot action. Instead of making the mpg worse (as you'd expect), once returning to the same speed you were previously travelling you find your average mpg then starts to climb. It's just as if the extra airflow gives the MAF (or maybe the MAP) a sort of kick start which starts it working correctly. This gives the very strong impression that the ECU is learning.

I've noticed this when travelling at 70mph (and really struggling to maintain 55mpg) - then with a quick blast up to 80 and back down to 70 the average mpg starts rising to 60mpg

Similarly when maintaining 80 but struggling to even return 45mpg, a sudden blast up to (I wont even mention it ) then the mpg starts climbing up to 50mpg

Interestingly, good consumption is NOT lost when stopping at say a service station (presumably as the engine remains warm) but is always lost if left overnight etc.

If you think about it then this suggest (for me at least)

• There's little point trying to drive economically
• Fuel consumption on short journeys is likely to be dire (even worse than you'd expect)

That said, I've managed a new consumption record:

Poole to Folkestone town centre = 172 miles @ 64.1mpg

......but once I get a new MAF then I'm going to try to improve on that

RJose said:

Hi Argo, I love to read your posts. The engine effort to give power to the wheels and keep the car moving is by far higher than just idling. When cruising you have several opposite forces that you don't have in idle mode, and on that low speed your car is struggling to keep it going. I don't mean that you can't run on that rev or speed with that gear, I do low revs all the time, I rarely rev higher than 2k (just when I'm flooring it), but of course I know that, on so low rev speeds, I can only accelerate very slowly and never put the car on climb hill stress
Nevertheless I just saw that you have the stilo remapped, ok, 150hp must be different from the 115hp, I'm sure of that Maybe the car get a little different behavior. Feel free to share your experience with the 150 stalions

Click to expand...

Thanks for the good vibes

I'm sure you're right but discussion the correct gear at low speeds is likely to be a long one (I know I'm always changing )

The remap from Angel Tuning drops torque a little at very low revs (1000rpm) so is not, in my view, ideal for great fuel consumption but as you can see it still does pretty good. My best before remap was 130 miles @ 62.5mpg

fuel consumption definatley better after EGR clean and new air and fuel filter

I have a 2002 115 JTD and my MPG is very very poor. Last week over 7 days my average was 28.6mpg, and that was sensible driving trying to improve it. First 2 days of this week and I'm averaging 22Mpg. What is going on here?

I had a preheat fault for the past 6weeks or so, which last night I found was a bad +ve to the glow plug relay (must have got very hot as there is melted plastic there.) I cut the connector and renewed it. Checked glow plug resistances whilst i was there and there all about 1 ohm (is this right?!) Anyway, now no preheat fault, but no improvement in MPG (infact worse, but maybe coincidental.)

I'll have a look at the air filter and MAF sensor tonight. Where do I find the MAP and EGR? Any other suggestions? Please help! Shes costing me a fortune at the minute!

Xen said:

I have a 2002 115 JTD and my MPG is very very poor. Last week over 7 days my average was 28.6mpg, and that was sensible driving trying to improve it. First 2 days of this week and I'm averaging 22Mpg. What is going on here?

Click to expand...

I didn't think it was possible to get it that low.

I suppose you have verified the figure with a real tank to tank check ?